A vehicle such as an automobile is generally equipped with airbag devices for inflating and deploying airbags in the vehicle and absorbing the impact on occupants in an emergency such as a collision or sudden deceleration. Various types of airbag devices have been developed and are used, for example, an airbag device for a driver's seat mounted in the steering wheel, an airbag device for the front passenger seat mounted in the instrument panel, a side airbag device mounted in the side of the vehicle or in a seat, a curtain airbag device mounted in the upper parts of doors, and a knee airbag device for the knees of an occupant.
These airbag devices generally have an airbag and an inflator. The airbag is normally folded and that is inflated and deployed in an emergency, and the inflator supplies gas to the airbag. During a collision or sudden deceleration of the vehicle, gas is supplied from the inflator to the airbag to inflate and release the airbag in the vehicle, inflating and deploying the airbag.
In such airbag devices, there is often a need to dispose airbags (inflation chambers) that reduce impact or restrain occupants at a plurality of places, for example, to protect the head and the torso, the chest and the hip, occupants in a front seat and a rear seat, or an adult and a child. This need is high especially in side airbag devices and curtain airbag devices. In an airbag having a plurality of inflation chambers, when an occupant contacts the airbag, a gas flow occurs between the inflation chambers, thereby making it sometimes difficult to maintain sufficient internal pressure. In view thereof, check valves for an airbag described in Japanese Unexamined Patent Application Publication Nos. 2001-63502 and 2009-537360 have already been proposed.
In the check valve for an airbag described in Japanese Unexamined Patent Application Publication No. 2001-63502, a funnel-shaped (see FIG. 1 of Japanese Unexamined Patent Application Publication No. 2001-63502) or tubular (see FIG. 4 of Japanese Unexamined Patent Application Publication No. 2001-63502) flow path is formed by disposing an intermediate cloth between a first chamber and a second chamber. When gas flows in one direction, the check valve allows gas to flow. When gas flows in the opposite direction, the intermediate cloth blocks the flow path to prevent the flow of gas.
The check valve for an airbag described in Japanese Unexamined Patent Application Publication No. 2009-537360 is formed by a double layer formed in a flow duct. One layer of the double layer is pressed against the wall on the opposite side, thereby blocking the flow duct (see FIG. 2 of Japanese Unexamined Patent Application Publication No. 2009-537360).